Positive drug test scenarios – oral fluid collection
The scenarios below describe the likely patterns of behaviour common to many drug, medication or alcohol users. These are shown with the likely observations arising for both screening and confirmation tests when it comes to oral fluid tests.
What are the baseline numbers?
This form of testing is predicated on the following assumptions:
Oral fluid screening tests detect:
opiates (at 50µg/L)
amphetamine-type stimulants (50µg/L)
cocaine and metabolites (50µg/L)
cannabinoids (THC – 15µg/L)
benzodiazepines (10µg/L)
oxycodone (40µg/L)
Furthermore, the usual windows of detection are:
AMP, MET, OPI (and OXI), and COC all within minutes following consumption for up to 3 to 4 days, depending upon dose.
BZO within minutes following consumption for up to 3 days, depending upon dose and identity of drug.
THC (smoked or vaped) within minutes following consumption for up to 7 to12 hours.
THC (capsule or melt/gel) within minutes following consumption then undetectable after 30 minutes.
Oral fluid confirmation tests detect:
opiates, cocaine metabolites, and amphetamine-type stimulants (25µg/L)
cannabinoids (THC – 5µg/L)
benzodiazepines (2µg/L)
oxycodone (20µg/L).
Furthermore, the usual windows of detection are:
AMP, MET, OPI (and OXI), and COC within minutes following consumption for up to 3 to 5 days, depending upon dose.
BZO within minutes following consumption for up to 3 to 4 days, depending upon dose and identity of drug.
THC (smoked or vaped) within minutes following consumption for up to 7 to 12 hours,
THC (capsule or melt/gel) within minutes following consumption then undetectable after 30 minutes.
Scenario A
A worker has a valid prescription for lisdexamphetamine (3mg/day to treat ADHD). They also use methamphetamine and took this illicit drug at midnight. The following morning (0800) they provided an oral fluid specimen.
The screening test may be initially unsuccessful in collecting a valid oral specimen (dry mouth) even with drinking water provided. The result will be non-negative for both MET and AMP. The donor may claim the result is due to prescribed medication. The specimen is required to be confirmed at the laboratory. The dry mouth is a consequence of the decongestant effect of amphetamine-type stimulants.
Laboratory results may show MET at over 1200µg/L and AMP at 400µg/L. This is consistent with use of methamphetamine. The AMP is a consequence of both prescribed lisdexamphetamine, and the amphetamine derived from MET metabolism. There are no medications containing methamphetamine in Australia. This will be a positive illicit drug test result.
Scenario B
An employee has found information online that suggests rinsing the mouth with apple cider vinegar will defeat an oral fluid drug test. As an occasional cannabis smoker who had consumed cannabis the evening prior, and expecting to be tested at work, he has this material in his locker and when he is called to provide a specimen, he briefly rinses his mouth with vinegar and attends the testing room.
The test procedure requires the collector to ask the donor if they have had anything by mouth (food, drink, smoking, etc.) in the previous 10 minutes. Documents are completed (consent forms, test record forms) and signed and the collector looks into the worker’s mouth to check there is nothing present.
At 5 minutes the worker is asked to use an oral fluid device to collect oral fluid. The screening test will be non-negative for cannabinoids, and a specimen will be collected for laboratory confirmation.
The laboratory results may show THC at 22 to 50µg/L. This is consistent with use of cannabis no more than 7 to 12 hours prior to collection. The period of impairment parallels that of oral fluid detection. This will be a positive illicit drug test result for cannabis.
The mouth clears itself of materials (such as food, drinks, etc) within about 3 minutes so the collection process allows sufficient time to eliminate any residue.
In addition, if the collector were to notice any residue (visible or by odour) they will note this on the testing form and the worker may be found in breach of the drug policy for adulteration of a specimen.
Scenario C
A worker experiencing back pain overnight took two Panadeine Forte capsules, prescribed to her partner. The worker is required to complete a drug test at 9.30am.
The onsite screening test will be non-negative for opiates. A specimen will be dispatched to the laboratory and the worker stood down from duties pending the test result.
The laboratory will confirm codeine (at greater than 1200µg/L) and morphine (at about 600µg/L). This would be consistent with the use of codeine medication, but with no prescription held by the worker, this would be recorded as a breach of policy and the worker liable to disciplinary action.
Scenario D
An employee has a valid prescription for a cannabidiol (CBD oil) medication. They also smoke cannabis regularly because they believe they already have the CBD prescription, and this will explain any positive test results.
The onsite screening test will be non-negative for cannabinoids. The worker may claim that they have a prescription, but a specimen will be sent to the laboratory for confirmation in any case. The worker may convince the manager that it is medication-related to be able to remain at work until the drug test result is available.
The laboratory will confirm THC (likely at greater than 1200µg/L). This would be inconsistent with the use of CBD medication and would confirm illicit cannabis use, possibly as recently as 2 hours prior to sample collection.
In addition, the worker’s actions to remain at work and falsify their explanation for the non-negative test may represent gross misconduct and the worker’s employment could be terminated.
Scenario E
A worker consumes cocaine as they arrive at their worksite and before commencing their shift. They are tested by oral fluid 30 minutes later.
Onsite screening test will be non-negative for COC. The worker declares cold and flu medication. A specimen is dispatched to the laboratory for confirmation and the worker is stood down from duties pending results.
The laboratory will confirm cocaine and metabolites exceeding 2000µg/L. Cocaine is rapidly absorbed and distributed and appears in oral fluid within minutes of use. There are no medications containing cocaine permitted in Australia.
The scenarios and rationales provided above act as a demonstration of the skills and expertise in professionals examining drug and alcohol test results and the principles applied in reaching conclusions. They also Inform workers and business clients of the level of detail available to Toxicologists and MROs from inspection of drug and alcohol test results, and highlight the capabilities of these professionals in real world interpretations of evidence.
Understanding these capabilities may act as a deterrent to the consumption of drugs and alcohol by workers who will appreciate the likelihood of accurate detection.
Finally, client businesses and managers of drug and alcohol programs may use these scenarios as examples to illustrate behaviours that lead to positive drug and alcohol detections.
AusHealth toxicology provides technical and specialist advice to client businesses regarding drug and alcohol testing policies and procedures, and all technical aspects of the Australian standards.